1. Field of the Invention
The present invention relates to a method and apparatus for computer-assisted-design (“CAD”) of piping systems. In particular, the invention relates to a CAD method and apparatus suitable for creating swing-joint intersections between sections of piping in a three-dimensional drawing.
2. Description of the Related Art
The design of a layout area consisting of layout piping objects, such as water delivery pipes for use in a fire sprinkler system, requires the interconnection of the pipes arranged in three dimensional space. When two pipes must interconnect it is desirable to design the layout so that the connections may be formed at 90° angles rather than bends. This design enables the pipes to be assembled, in an actual construction, using standard “elbow” fittings which typically include a 90° change in direction. By using two 90° degree changes of direction, a pipe can jog-over to interconnect with another pipe. This connection is a “swing-joint”.
In conventional systems for the CAD layout of piping systems, swing-joints are manually determined by the designer while he/she watches the design drawings and data. The decision as to which layout objects should be relocated, in what sequence, and by what amount of movement is left to the operator. As a result, it takes a great deal of the designer's time and effort to create swing-joint intersections in the design layout. Swing-joint intersections are particularly difficult to calculate manually because pipe layout object segments must be modified to arrive at that point, in three dimensional space, where the pipes can be interconnected with elbow fittings. Moreover, after modification of the pipe layout object segments, it is time consuming to consolidate the modified arrangement of segments into a design layout which is efficient for application in an actual construction.
Computer assisted design systems which automate some of the decision making processes are also well known. For example, Mitsuta, et al., U.S. Pat. No. 4,831,546, discloses a design system for routing piping (in the layout planning of building installations a method of optimally determining the optimal piping route relative to interfering objects by entering data of installation layout, layout objects, and data of design reference) and, Yoshida et al., U.S. Pat. No. 4,992,953, discloses a computer assisted design method and apparatus for finding and displaying a graphic pattern of a liquid stay area (layout object data relating to the layout object specified by an input device and a liquid discharger arrangement rule). However, with these design systems, changes in direction are simply located where the piping bends to overcome the interfering or arranged objects in the design layout.
Thus, what is needed is a method and apparatus which is suitable for creating swing-joint intersections between sections of piping in a three-dimensional CAD drawing. There also exists a need for a system which enables the designer to rapidly create swing-joint intersections, in a three dimensional CAD piping design layout, among user specified layout objects depicted in the design display. A further need exists for an automated method and apparatus which is useful to mathematically determine the optimal locations for turning the piping in order to create the swing-joint intersections in three dimensional space and to modify and consolidate the piping layout object segments for use in an actual construction. The disclosed invention satisfies these needs.